The objective of the proposed research is to develop atraumatic, low prime, high capacity blood oxygenation systems for partial or total support during prolonged periods of respiratory insufficiency. The current work includes studies of (1) novel gas transfer techniques, efficient fabrication methods, and design theory for membrane oxygenators and (2) coagulation control during extracorporeal bypass. Three techniques for achieving high gas-transfer rates are being explored: two involving the blood phase transfer and one the membrane- phase transfer. The blood phase studies are of secondary flows in a Taylor-Vortex unit and in a Coriolis force unit. The membrane-phase study is of the advantages of transient-state gas transport. A semiautomatic fabrication method is being developed for tubular units. Design optimization calculations have been completed for both tubular and sheet units. Coagulation control studies include experiments to delineate factors that affect heparin potency during prolonged extracorporeal bypass.